My earlier LP detector put the solenoid in series with the ground connection.
My replacement fro Safe T alert, a combination LP detector and co2 sensor does not. It requires you connect a relay input to the in coming power. Then the relay sends power to a new solenoid. Safe T alert says that the original solenoid would not handle the full 12 volts put out by their detector.
Do you see the make of your old detector?
What is make and model of new detector?
Look at the solenoid next to your LP tank and check wiring from detector.
